<!DOCTYPE html>
<html lang="en">
  <head>
    <meta charset="UTF-8" />
    <meta http-equiv="X-UA-Compatible" content="IE=edge" />
    <meta name="viewport" content="width=device-width, initial-scale=1.0" />
    <link rel="stylesheet" href="./styles/index.css" />
    <title>综合案例-成绩案例</title>
  </head>
  <body>
    <div id="app" class="score-case">
      <div class="table">
        <table>
          <thead>
            <tr>
              <th>编号</th>
              <th>科目</th>
              <th>成绩</th>
              <th>操作</th>
            </tr>
          </thead>
          <tbody v-if="list.length > 0">
            <tr v-for="(item, index) in list" :key="item.id">
              <td>{{index + 1}}</td>
              <td>{{item.subject}}</td>
              <!-- 需求：不及格的标红， < 60分，加上 red 类 -->
              <td :class="{red:item.score < 60}">{{item.score}}</td>
              <td><a href="http://www.baidu.com" @click.prevent="del(item.id)">删除</a></td>
            </tr>
            
          </tbody>
          <tbody v-else>
            <tr>
              <td colspan="5">
                <span class="none">暂无数据</span>
              </td>
            </tr>
          </tbody>

          <tfoot>
            <tr>
              <td colspan="5">
                <span>总分：{{totalScore}}</span>
                <span style="margin-left: 50px">平均分：{{avgScore}}</span>
              </td>
            </tr>
          </tfoot>
        </table>
      </div>
      <div class="form">
        <div class="form-item">
          <div class="label">科目：</div>
          <div class="input">
            <input
              type="text"
              placeholder="请输入科目"
              v-model.trim="subject"
            />
          </div>
        </div>
        <div class="form-item">
          <div class="label">分数：</div>
          <div class="input">
            <input
              type="text"
              placeholder="请输入分数"
              v-model.number.trim="score"
            />
          </div>
        </div>
        <div class="form-item">
          <div class="label"></div>
          <div class="input">
            <button class="submit" @click="add">添加</button>
          </div>
        </div>
      </div>
    </div>
    <script src="https://cdn.jsdelivr.net/npm/vue@2/dist/vue.js"></script>

    <script>
      const app = new Vue({
        el: '#app',
        data: {
          list: [
            { id: 1, subject: '语文', score: 20 },
            { id: 7, subject: '数学', score: 99 },
            { id: 12, subject: '英语', score: 70 },
          ],
          subject: '',
          score: ''
        },
        computed:{
          totalScore() {
            return this.list.reduce((sum, item) => sum + item.score,0)
          },
          avgScore() {
            if(this.list.length === 0) {
              return 0
            }
            return (this.totalScore / this.list.length).toFixed(2)
          }
        },
        methods:{
          del(id) {
            this.list = this.list.filter(item => item.id !== id)
          },
          add() {
            if(!this.subject) {
              alert('请输入科目')
              return
            }
            if(typeof this.score !== 'number') {
              alert('请输入正确的成绩')
              return
            }
            this.list.unshift({
              id:+new Date(),
              subject:this.subject,
              score:this.score
            })
            this.subject = ''
            this.score = ''
          }
        }
      })
    </script>
  </body>
</html>
